1. Field of the Invention
The present invention relates to coupling apparatus and method of use for joining together electrical conduit in a conduit system. The coupling apparatus includes a resealable port for introducing lubrication therein in order to facilitate wire pulling through the conduit system and to reduce strain on the wire insulation material.
2. Brief Description of the Prior Art
The installation of electrical conduit systems in homes and commercial buildings is a labor intensive job. An especially labor intensive task is the feeding and pulling of a bundle of insulated wire through a conduit run.
In the usual case, the wire pulling operation requires at least two or more workers to feed and pull the wire through the conduit run. The wires are attached together at one end to form what is known in the trade as the "head" or "head portion". The head, in turn, is attached to a feeder rope or fish steel which is threaded through the conduit run to assist in pulling the wire therethrough. A first worker at the beginning of the conduit run forms a number of wires coming off separate spools into a bundle with the wires preferably oriented side by side (i.e., the wires do not cross over each other). The worker then feeds the bundle of wire into the conduit system while one or more other workers pull on the feeder rope at the end of the conduit run thereby drawing the wire through the conduit.
Friction between the wire bundle and the inner conduit surface is a major problem which is encountered during the wire pulling operation. Care also must be taken to ensure against damaging the wire insulation. Accordingly, it is necessary to provide sufficient lubrication to the wire bundle as it is being pulled through the conduit run. The head portion, in particular, being a very stiff portion of the wire bundle, presents the greatest source of friction. In accordance with the conventional practice, lubricant is only applied to the head portion of the wire bundle at the beginning of the conduit run. Lubricant applied in this manner tends to wear thin and become ineffective after only a short pulling distance. This increases the strain on the wire being pulled through the conduit system and also requires that the workers pull harder in order to keep the wire bundle moving through the conduit.
Friction is even more problematic in logistically complex conduit runs, such as those commonly found in the ceilings of commercial buildings, which typically have many bends and curves in order accommodate the pre-existing fixed structures in the building, such as, for example, trusses, beams, HVAC hardware, plumbing hardware and the like. The presence of such fixed structures make a straight line conduit run impossible or impractical. If, during the wire pulling procedure, the head gets snagged on some bump or imperfection in the interior surface of the conduit or gets stuck in the middle of a bend in the conduit run, all pushing on the wire bundle must be stopped as the continued pushing only causes the wire bundle to bunch up and the individual wires to cross over each other. This causes the diameter of the wire bundle to expand which, in turn, increases friction and complicates the wire pulling operation. If the friction on the head and wire becomes to great, the pulling strain on the conduit system can quickly exceed recommended safety margins. More importantly, the increased friction can break down the wire insulation and thereby adversely effect the insulation's di-electric value.
In lengthy conduit runs or in conduit runs which contain 180.degree. bends or where the wire size is 1/0 cm or larger, a pulling motor is required to pull the wires through the conduit system. The conduit system will give warning by making groaning and creaking noises when there is excessive friction. In this situation, the pulling force must be reduced. This increases the time and effort it takes to complete the job. It would therefore be desirable to be able to reapply lubrication to the head of the wire bundle at selected locations in a conduit run in order to reduce friction on the head and thereby facilitate safe and efficient wire pulling through the conduit run during an installation or repair or remodel.
It would further be desirable to incorporate a means for introducing lubricant at one or more conduit couplings in a conduit run so that the installation for a conduit system can be planned with a sufficient number of lubrication points to ensure low friction and trouble free wire pulling therethrough.
Conduit fittings having removable plates which permit access to an interior portion of the conduit body are known from the prior art. These conduit fittings are designed for use in exposed conduit applications which allow convenient access by a worker. Such conduit fittings typically have enlarged diameter central body portions or other structure such as large diameter adjoining pipe sections which present snag points for the head portion of a wire bundle being pulled therethrough. In other words, the prior art fittings do not have sufficient internal structure in the conduit body to guide the wire through the conduit fitting without human assistance.
Accordingly, there is a definite need in the art for a conduit coupling which includes means for permitting the introduction of lubricant and wherein the wire being pulled through the conduit coupling is self-guiding.